The present invention relates to a mineral wool waste cement and more particularly to a cement that includes, as an addition, i.e. a partial portland cement replacement, various waste materials resulting from the production of mineral wool.
It has been known for many years that various additives can be used as a partial replacement for portland cement to more economically make cementitious products without compromising the long term strength properties of such products.
Ground furnace slags have been used as a replacement or additive to portland cement since the late 1800's. Since that time the slags from blast furnaces, steel furnaces, copper furnaces, phosphate furnaces, etc. have all been used in different forms for such purposes. They have been added to portland cement clinkers in various percentages and interground, or they have been ground separately and blended with portland cement.
For example, U.S. Pat. No. 1,916,157 describes a cement consisting of portland cement and cupola slag, which is different from blast furnace slag that is also used in cement manufacture. U.S. Pat. No. 3,582,377 discloses the use of "non cement" materials as substitutes for portland cement or silica flour to make precast masonry products. Specifically there is described the use of ordinary air-cooled blast furnace slag to produce masonry blocks, although theretofore such air-cooled slag was not considered acceptable for such purposes. U.S. Pat. No. 3,825,433 describes the use of "phosphorus furnace slag" and portland cement for making concrete. U.S. Pat. No. 4,451,295 describes an improved cement for making concrete and mortar. The cement comprises a mixture of calcium carbonate or portland cement kiln dust, or both, and ground granulated blast furnace slag.
In addition to furnace slags, other materials have been added to portland cement to make concrete and masonry products. U.S. Pat. No. 3,202,522 describes the dispersion of asbestos fiber, preferably about 10%-40% by weight, throughout cementitious materials or constituents, including a slag cement component. The fiber acts as a mechanical reinforcement, as in common asbestos portland cement compositions or products thereof. U.S. Pat. No. 3,823,021 describes a cement composition and an addition for use in hydraulic cementitious mixtures, such as grouts, mortars and concrete. The composition comprises as a cement, silica sand and soda lime glass particles having a size within a specified range.
In recent years there has been broader acceptance and greater confidence in the performance of interground and blended slag-portland cements. In Europe the production of slag cements represents 20% of total cement production. Although, for many years, the cement industry in the United States resisted acceptance of additives because of the erosion it caused in prices, more recently the industry has accepted the use of cement additives in order to more economically manufacture products that can compete with the prices of imported cement.
There is contained in U.S. Pat. No. 3,096,188, a disclosure of a composition material adapted to use previously discarded portions of comminuted blast furnace slag. A granular slag is produced by quenching a molten blast furnace melt, rich in silicic acid, in an agitated cooling fluid to form a sharp edge glassy sand having large brittle grains. The sand is crushed to specified particle size and mixed, in a specified range, with water and a hydraulic binder, such as portland cement, gypsum or lime.
U.S. Pat. No. 3,615,783 discloses a hydraulic cement that uses, in combination with portland cement, a mineral wool manufacturing by-product, which is made from modified blast furnace slag. In the process of manufacturing mineral wool, blast furnace slag is remelted with the addition of silicon dioxide and alumina, which has a ratio of silicon dioxide substantially higher than lime. The remelted slag plus additions is referred to as modified slag. The modified slag is discharged from the furnace, under the influence of steam and air cooled. About half of the modified slag is formed into fibers commonly referred to as "mineral wool" and collected, while the residue, known as mineral wool shot or shot slag, is precipitated and discarded. In contrast to prior belief, the patentee found that the shot slag, with the ratio of silicon dioxide substantially higher than lime, is virtually 100 percent glass, and has excellent latent hydraulic cementicity. The shot slag, reduced to a finely divided state, and mixed with portland cement, can be used in varying ways to produce a hydraulic cement product.
Thus it has been known to use, as described above, various additives as a partial replacement for portland cement to more economically make cementitious products. And it has been known to use modified shot slag, having a ratio of silicon dioxide substantially higher than lime, a by-product of the mineral wool manufacturing process, as an additive for portland cement to make a hydraulic cement product. However, there remain substantial wastes, other than shot slag, which are found as by-products of mineral wool plants and for which heretofore no use has been found. As a consequence, mineral wool plant waste material from a variety of locations within such a plant are presently discarded and dumped on unsightly refuse piles that adjoin the plants.